Communication networks generally comprise a number of communication nodes that are interconnected using some form of communication medium. For example, a local area network (LAN) is a communication network that includes a number of user terminals in a relatively localized area that are interconnected amongst each other by a network medium such as a twisted pair or coaxial cable. Communication networks can also be connected to other communication networks so that users of one connected network can communicate with users of another connected network. An example of this is the Internet which consists of a large number of individual networks that are connected to one another through a high capacity backbone medium. Individual communication networks can also be subdivided into a number of subnetworks that each consist of a subgroup of the total nodes in the network. For example, a large corporation having many different buildings may maintain a different subnetwork for each building. The subnetworks are then interconnected to form the corporate network. The individual subnetworks are often separately addressable entities that can be individually managed.
Oftentimes, it is desirable to insert a server or other type of network device within an individual link in the network so that all communications through that link pass through the server. An example of this would include the insertion of a firewall device within the connection path between two networks or subnetworks, such as between a private network and the Internet. A firewall device is essentially a filter that controls the type of information that can flow into or out of an individual network. For example, a corporation whose corporate network is connected to the Internet may install a firewall within the connection to prevent external entities from having access to the corporation's internal files. The corporation's firewall can also be used to control which extra-corporate resources the corporations employees will have access to.
A network server that is located within an individual link of a network can create a problem if the server fails during network operation. That is, the failure will generally sever the connection between the nodes on either side of the network link. If a firewall device fails, for example, the two networks attached thereto will no longer be able to communicate with one another. Many times, such network links are critical to an entity's business activities and must operate without interruption. For this reason, many businesses are reluctant to install servers within these critical links. Failure to install such servers (such as, for example, a firewall) may compromise network security, which can produce equal or greater harm to the entity.
Therefore, a need exists for a method and apparatus that allows uninterrupted service through a network link having a server, even if the server fails.